The locations work fine when I test "london uk" as my search address. Seems you have this resolved.
The response is very slow, BTW. The site is extremely "heavy" with the theme you are using which is making a number of incorrect calls to the Google Font library in addition to the image servers for doubleclick and other images loading slowly. The biggest problem is the incorrect Google Font library implementation.
Envato/Theme Forest theme by any chance? I've been seeing a lot of issues lately with Theme Forest themes using Google Fonts incorrectly and causing severe response issues on sites, which makes it look like store locations are not coming back.
All support for SLP is moving to the CSA website. Posts on that site now take precedence and get my attention first. Visit the new support forum here: